Ticked off

Ever since I bought the Ultra in '07 I have heard a faint ticking noise on the headset when the sound is over the speakers but the headset cable still connected.
I use this configuration as I have a telephone interface and make frequent calls through it.
The bike has been back to the dealership several times and on the last visit the headset, wiring harness and radio have been replaced aswell as filters being installed. It must be engine noise as it speeds up with it.
Dealer doesn't know, Harley Uk and US have no idea and I'm sick of it.
Does any other '07 Ultra owner have this problem? Or does anyone have an idea?

I do not have a telephone interface, but I do have a Nextel phone that is always on my hip. The phone will cause interference with the radio if I am getting a call or a message. You have probably already tried to trouble shoot this, but I would start by disconnecting the phone and leaving it at home once to see if you still have it. Just my thought.....

That's what the dealer suggested. He had the bike in for 6 weeks and came up with that. He didn't realize that when I was at home and he could still hear the ticking that it must be something else. Unfortunately it's something more uncommon.
I thought at first that it could have been the cd player's motor but as I said it speeds up.

Yes I am. As the warranty was about to run out he had to replace some rusting parts. (again) See list.Both mirrorsBoth wheelsPannier bracketsBracket boltsBoth front forksBoth exhaustsBoth exhaust heat shieldsFront fender bracketsFront wheel axleRadio wiring harnessHeadsetsTop box hingesIgnition leadsSpark plugsRadio
Don't ask me what I think of the quality of the Harley Davidson I bought. And now it doesn't even run anymore either.